Drug abuse treatment that incorporates adequate doses of daily methadone and weekly counseling is usually effective in managing the pervasive and devastating symptoms of opioid dependence (e.g., Simpson & Sells, 1990). Over two-decades of treatment research has also shown that the presence of a comorbid psychiatric disorder adversely impacts the overall effectiveness of this treatment modality, at least for many of these unfortunate patients (King et al., 2001; Rounsaville et al., 1986). Interventions with much hope of resolving this serious health problem must ultimately change the fact that most of these patients fail to receive any psychiatric care -- even when referred to general psychiatric settings outside of the drug abuse program. The extremely poor patient adherence to psychiatric care is a major health services problem that reaches across patients, programs and countries (e.g., Thompson et al., 2000). One promising approach to reducing the poor adherence that exposes these drug abusers to unnecessarily high levels of morbidity from untreated psychiatric disorders is a fully integrated service delivery approach. Using an integrated model of care, drug abusers with a comorbid disorder could be offered a broad range of standard psychiatric services with the drug abuse program. While practitioners and researchers extol the virtues of integrated systems of drug abuse and psychiatric care, amazingly few controlled studies have been done to evaluate the efficacy of this approach (e.g., Drake et al., 1996, Ley et al., 2001). More importantly, most of these studies were conducted in general psychiatric versus drug abuse programs, and the small number done in drug abuse settings did not use random assignment to evaluate the influence of on- versus off-site services on adherence or outcomes; and all but one of these studies (Saxon et al., 1995) offered a very narrow range of services. The proposed work will be the first known randomized evaluation of the effectiveness of an integrated drug abuse and standard psychiatric treatment approach delivered a drug abuse program. Study participants will be 396 opioid abusers with a current psychiatric disorder; all will be new admissions to the Addiction Services Treatment program (ATS). Using a two-group factorial design, participants will be randomly assigned to either the Integrated Substance Abuse and Psychiatric Care condition (ISAP-Integrated) or the Parallel Substance Abuse and Psychiatric Care condition (PSAP-Parallel). Participants in the ISAP condition will be offered standard psychiatric care in the ATS program; those assigned to the PSAP condition will be offered care in the Community Psychiatry Program (CPP), located on the same campus. The scope and amount of standard psychiatric services will be the same across treatment sites (ATS and CPP); all drug abuse services will be provided in the ATS program. Participants will be evaluated over a 12- month period and compared on a range of adherence and outcome measures: rates of initial engagement in psychiatric care and overall adherence to psychiatric services (therapy sessions and prescribed medications), adherence to scheduled drug abuse treatment services, and a range of objective and self-reported psychiatric and drug abuse treatment outcomes, including utilization rates of high cost intensive ambulatory psychiatric care, acute inpatient psychiatric hospitalization, and emergency room visits for psychiatric or drug abuse problems. This study will produce both timely and scientifically rigorous health services research data on the effectiveness of integrated psychiatric and drug abuse treatment in a drug abuse program; data from this study will inform and guide the treatment field and both local and national health care discussions and decisions that will impact the organization and funding of drug abuse and mental health services.